The present invention relates to a process for forming a releasable metal layer on a metal carrier substrate, and more particularly to a process involving both vapor deposition and electrodeposition to form a releasable copper layer on a carrier substrate.
In the electronics industry, increased functionality continues to be integrated into smaller, lighter, and less costly electronic devices. The width of the copper trace lines on a printed wiring board (PWB) has a significant influence on the size of the printed wiring board, and the amount of functionality that can be crammed into the allotted space. Accordingly, the electronics industry continually strives for finer lines and spaces to provide smaller, lighter and less expensive electronic devices having greater functionality. The minimum width of the copper trace lines attainable by a subtractive etching process is strongly influenced by the thickness of the copper foil on the surface of the laminate. Thinner copper foil enables the fabrication of narrower trace lines.
Further, in this regard, multi-layer PWBs increasingly use microvia technology to make interconnections between conductive layers. A microvia is generally defined as a via (xe2x80x9celectrical pathxe2x80x9d) that is less than 0.1 mm in diameter between two layers of a circuit board structure. The microvias are preferably produced by a laser that xe2x80x9cdrillsxe2x80x9d small holes through layers of the PWB. It has been found that copper foil having a thickness less than 5 xcexcm is more advantageous than thicker copper foils in a laser drilling process, in that lasers currently used in forming microvias more easily drill through thin copper foil than thicker copper foils. Thus, thinner copper foils are more desirous in forming multi-layer printed wiring boards in that they facilitate finer trace lines and are easier to drill using present laser processes.
The present invention relates to a method of forming thin copper foil on a carrier substrate, which copper foil is for use in forming printed wiring boards.
In accordance with the present invention, there is provided a method for producing a releasable copper foil on a carrier substrate. The method includes the steps of: (a) vapor-depositing a layer of copper onto a carrier substrate having a separation facilitating layer formed thereon, wherein the vapor-deposited layer protects the separation facilitating layer during subsequent processing; and (b) electrodepositing a layer of copper onto the vapor-deposited layer of the metal, thereby increasing the thickness of the copper layer.
According to another aspect of the present invention, there is provided a component for use in forming a printed wiring board, comprising: a carrier substrate; a separation facilitating layer formed on the carrier substrate; a vapor-deposited layer of copper on the separation facilitating layer, wherein the vapor-deposited layer protects the separation facilitating layer; and an electrodeposited layer of copper on the vapor-deposited layer.
It is an object of the present invention to provide a thin copper foil for use in forming a printed wiring board.
It is another object of the present invention to provide a releasable thin copper foil on a carrier substrate having a separation facilitating layer.
It is another object of the present invention to provide a releasable thin copper foil on a carrier substrate having a protective layer of vapor-deposited copper for protecting a separation facilitating layer during subsequent processing.
It is another object of the present invention to provide a thin copper foil on a carrier substrate as described above, that can be easily handled.
Another object of the present invention to provide a thin copper foil that enhances the yield and productivity of a PWB production process.
A still further object of the present invention is to provide a novel process for manufacture of a relatively thin copper foil.
A still further object of the present invention is to provide a process for manufacture of a thin copper foil on a carrier substrate that has reliable releaseability from the carrier.
Yet another object of the present invention is to provide a process as described above for manufacture of a thin copper foil that has a relatively low porosity.
These and other objects will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings and the appended claims.